Function processCohortData

packages/db/src/services/retention.service.ts:447–504

(
  data: Array<{
    cohort_interval: string;
    total_first_event_count: number;
    [key: string]: number | string;
  }>,
  diffInterval: number,
  interval: IRetentionInterval = 'day',
  until?: string
)

// the row is internally consistent: period 0 equals Total profiles and the
// curve starts at 100%.
export function processCohortData(
  data: Array<{
    cohort_interval: string;
    total_first_event_count: number;
    [key: string]: number | string;
  }>,
  diffInterval: number,
  interval: IRetentionInterval = 'day',
  until?: string
): IRetentionCohortRow[] {
  if (data.length === 0) {
    return [];
  }

  const columns = range(0, diffInterval + 1);
  const processed = data.map((row) => {
    const sum = row.total_first_event_count;
    const values = columns.map(
      (index) => (row[`interval_${index}_user_count`] || 0) as number
    );

    return {
      cohort_interval: row.cohort_interval,
      sum,
      values,
      percentages: values.map((value) => (sum > 0 ? round(value / sum, 2) : 0)),
    };
  });

  const maturePeriods = processed.map((row) =>
    maturePeriodCount(row.cohort_interval, until, interval)
  );
  const totalSize = processed.reduce((acc, row) => acc + row.sum, 0);
  const representativeSize = round(totalSize / processed.length, 0);

  const averageRow: IRetentionCohortRow = {
    cohort_interval: 'Weighted Average',
    sum: representativeSize,
    values: [],
    percentages: [],
  };

  for (const index of columns) {
    let matureSize = 0;
    let retained = 0;
    processed.forEach((row, i) => {
      if (index <= maturePeriods[i]!) {
        matureSize += row.sum;
        retained += row.values[index]!;
      }
    });
    const rate = matureSize > 0 ? retained / matureSize : 0;
    averageRow.percentages.push(round(rate, 2));
    averageRow.values.push(round(rate * representativeSize, 0));
  }

  return [averageRow, ...processed];
}